The American Casting Institutes' classical 12% chromium steel alloy designated as ACI CA-15 has been used for many years in the casting industry. It has always had serious disadvantages, particularly at higher carbon levels. These disadvantages include poor casting behavior, poor weldability and lower impact properties. The primary factor responsible for this condition is the relatively high allowable carbon content, which is in the order of 0.15%. It is well known that this level of carbon requires special handling in the foundry to remove gates and risers. In addition, preheat is necessary when welding to prevent cold cracking due to hard martensite formation in the heat affected zone.
Also it is known from field experience that with normal tempering temperatures, the cavitation resistance in equipment, such as pumps, or pump impellers, is not good. It is also known that cavitation resistance in general is a function of the hardness of the alloy, and in general the hardness of the alloy is a function of the carbon content.